Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
import queue
h, w = map(int, input().split())
d=[(0, 1), (1, 0), (0, -1), (-1, 0)]
s=[list(input()) for i in range(h)]
m=[[-1]*w for i in range(h)]
m[0][0]=1
q = queue.Queue()
q.put((0, 0))
while not q.empty():
    p=q.get()
    for i in range(4):
        x=p[0]+d[i][0]
        y=p[1]+d[i][1]
        if 0<=x<h and 0<=y<w and m[x][y]<0 and s[x][y]=='.':
            q.put((x, y))
            m[x][y]=m[p[0]][p[1]]+1
dis=m[h-1][w-1]
c=sum(si.count('.') for si in s)
print(c-dis if dis>0 else -1)